Golfers of all skill levels are constantly trying to improve their game and lower their score. Many take advantage of improved equipment such as golf clubs and golf balls. Golfers may even hire coaches to help fine tune the mechanics of their swing. Perfecting the mechanics of a golf swing is important because even small changes can greatly affect the trajectory of the ball.
Typically, a golfer wants to strike the ball such that it has desired kinematic characteristics, such as side spin, back spin, and velocity. A golfer can determine if their swing is producing the desired characteristics in many ways. One rudimentary method involves observing the golf ball after it has been struck by the club. A “good” shot typically reaches the location desired by the golfer. However, this method has its drawbacks. For example, a golf ball may reach a desired location even when it has less than optimal kinematic characteristics. Simply observing the golf ball with the naked eye doesn't allow a golfer to determine the kinematic characteristics of the ball or change their swing to achieve desired characteristics.
More advanced systems involve apparatus that are capable of imaging the golf club and/or golf ball in order to determine how a golfers swing affects the trajectory of the ball. These systems typically involve one or more imaging systems, lamps, reflectors, and motion detectors. Typically, these apparatus acquire images of the golf club and/or golf ball in motion. Once the images are acquired, they may be analyzed to determine the kinematic characteristics of the club and/or ball. These systems are useful because they can correlate the motion of the club with the resultant trajectory of the ball.
In many of these more advanced systems, the golf club and/or ball needs to be marked. Rudimentary markers may involve colored markers that are strategically placed on the surface of the golf club or golf ball. However, colored markers have several disadvantages. One disadvantage of colored markers is that they are difficult to distinguish because of background light, such as sunlight and the like. Another disadvantage of using colored markers is that they do not allow an imaging system to distinguish them from the color of the golf ball. Distinguishing the markers from the golf ball surface is important because measurements are determined based on the change in the position of the markers.
More advanced systems use retroreflective markers or limited spectrum markers that are placed on the surface of the golf ball or club. Retroreflective markers provide the advantage of reflecting light with a higher intensity than the light which they receive. Retroreflective markers however, have limited applications. One limitation of retroreflective markers is that they typically only reflect light on-axis. In other words, it is preferred that the light source strikes the markers on-axis. In response, the markers reflect light with the highest intensity on the same axis. This requires light sources and imaging systems to be properly positioned in order to achieve optimal results.
Limited spectrum markers may also be used on the surface of golf clubs or balls. Limited spectrum markers are typically only responsive to one wavelength of light. In response to a received wavelength of light, the markers emit light of a different wavelength. One example of a limited spectrum marker is a fluorescent marker. Fluorescent markers respond to a received wavelength by emitting a second wavelength of light. Using limited spectrum markers reduces the interference from ambient light because the wavelength of light emitted by the fluorescent markers may be filtered before being imaged. In other words, a filter may be placed before the imaging system such that light of only one wavelength, within a desired tolerance, may be imaged. This is especially helpful in situations that have high intensity ambient light, such as sunlight. Limited spectrum markers, however, have some limitations. For example, the imaging system must have a filter in order to isolate the light reflected by the markers. This may require a particular apparatus to be more complex or bulky. In addition, limited spectrum markers and filters must be chosen before testing begins, thereby reducing the adaptability of the apparatus.
Regardless of the type of markers that are used, they are typically placed in a desired pattern or orientation. It is usually desirable to orient the markers such that they are all visible to an imaging system. The number and pattern of the markers may altered based on the information that is desired. For example, it is common to position five markers at the vertices of a pentagon with one marker in the middle. The markers are then imaged at least twice. Golf clubs are typically imaged twice on the downswing, while golf balls may be imaged at least twice after impact. The changes in the position of the markers may then be analyzed, using a variety of well known algorithms, to determine the kinematic characteristics of the golf club and/or ball.
One limitation of using a marker, such as colored, retroreflective, or limited spectrum markers, is that they must be placed on the golf club or ball prior to using a particular apparatus. In addition, as described above, the markers are usually placed in a desired pattern and orientation prior to use. Thus, many apparatus available today do not allow a golfer to use their own equipment. Rather, a golfer must use the previously prepared golf clubs and balls that have markers placed on them.
A continuing need exists for a monitoring apparatus and method that does not require previously prepared golf clubs and/or golf balls.